Abradable and/or abrasive coating and brush seal configuration

Abstract

An abradable coating and/or an abrasive coating applied to the rotor of a steam or gas turbine allows the temperature and pressure drop capabilities of conventional brush seal assemblies to be increased. The pressure drop capability of brush seals is closely related to fence height, i.e., the distance between the rotor and the bottom edge of the backing plate supporting the brush seal wire bristles. Application of the abradable or abrasive coating allows the fence height to be reduced and the pressure capability of a brush seal assembly increased commensurately because the risk of the backing plate rubbing against the surface of the rotor, so as to cause damage to the rotor, is reduced. In addition, the backing plate can be made from a higher strength material that can withstand higher temperatures because any contact between the backing plate and the rotor results in no damage to the rotor, but rather a gradual reduction of the backing plate as it wears.

1 . A brush seal arrangement for a turbine including a brush holder assembly engaging a rotor of the turbine, the brush holder assembly comprising: 
 a plurality of wire bristles engaging a surface of the rotor;    a backing plate positioned on a first side of the wire bristles, the backing plate providing support for almost all of the length of the wire bristles;    a front plate positioned on a second side of the wire bristles, the wire bristles being positioned between the backing plate and the front plate; and    at least one of an abradable coating and an abrasive coating applied to a surface of the rotor, whereby application of the coating allows fence height to be reduced by serving to protect the surface of the rotor from damage in an instance where the backing plate rubs against the rotor.    
   
   
       2 . The brush seal arrangement of  claim 1 , whereby application of the abrasive or abradable coating further allows the backing plate to be made from a higher strength material that withstands temperatures greater than 950° F.  
   
   
       3 . The brush seal arrangement of  claim 1 , wherein an abradable coating is applied to the surface of the rotor, whereby contact between the backing plate and the surface of the rotor results in the abradable coating being worn, rather than in damage to the surface of the rotor.  
   
   
       4 . The brush seal arrangement of  claim 1 , wherein an abrasive coating is applied to the surface of the rotor, whereby contact between the backing plate and the surface of the rotor results in the backing plate being worn, rather than in damage to the surface of the rotor.  
   
   
       5 . The brush seal arrangement of  claim 2 , wherein an abradable coating is applied to the surface of the rotor, whereby contact between the backing plate and the surface of the rotor results in the abradable coating being worn, rather than in damage to the surface of the rotor.  
   
   
       6 . The brush seal arrangement of  claim 2 , wherein an abrasive coating is applied to the surface of the rotor, whereby contact between the backing plate and the surface of the rotor results the backing plate being worn, rather than in damage to the surface of the rotor.  
   
   
       7 . The brush seal arrangement of  claim 2 , wherein the backing plate is made from a material selected from the group consisting of austenitic stainless steel, ferritic stainless steel, nickel based superalloy, cobalt based superalloy, polymeric material and combinations of said materials.  
   
   
       8 . The brush seal arrangement of  claim 1 , wherein the abrasive coating is sprayed on.  
   
   
       9 . The brush seal arrangement of  claim 1 , wherein the abrasive coating is made from a material selected from the group consisting of alumina, chromium carbide and satellite.  
   
   
       10 . The brush seal arrangement of  claim 1 , wherein the abradable coating is sprayed on.  
   
   
       11 . The brush seal arrangement of  claim 8 , wherein the abrasive coating is made from a metallic material.  
   
   
       12 . The brush seal arrangement of  claim 10 , wherein the abradable coating is made from a metallic material.  
   
   
       13 . A brush holder assembly engaging a rotor of a turbine and having improved pressure drop and temperature capabilities, the brush holder assembly comprising: 
 a plurality of wire bristles engaging a surface of the rotor;    a backing plate positioned on a first side of the wire bristles;    a front plate positioned on a second side of the wire bristles, the wire bristles being positioned between the backing plate and the front plate; and    at least one of an abradable coating and an abrasive coating applied to a surface of the rotor;    whereby application of the coating to the surface of the rotor allows the backing plate to be made from a higher strength material that withstands temperatures greater than 950° F. and the distance between the bottom of backing plate and the surface of the rotor to be reduced by the coating serving to protect the surface of the rotor from damage in an instance where the backing plate rubs against the surface of the rotor.    
   
   
       14 . The brush holder assembly of  claim 13 , wherein the backing plate providing support for approximately seventy-five percent of the length of the wire bristles.  
   
   
       15 . The brush holder assembly of  claim 13 , wherein the backing plate is made from a material selected from the group consisting of austenitic stainless steel, ferritic stainless steel, nickel based superalloy, cobalt based superalloy, and polymeric material.  
   
   
       16 . The brush seal arrangement of  claim 13 , wherein the abrasive coating is sprayed on.  
   
   
       17 . The brush seal arrangement of  claim 13 , wherein the abrasive coating is made from a material selected from the group consisting of alumina, chromium carbide and satellite.  
   
   
       18 . The brush seal arrangement of  claim 13 , wherein the abradable coating is sprayed on.  
   
   
       19 . The brush seal arrangement of  claim 16 , wherein the abrasive coating is made from a metallic material.  
   
   
       20 . The brush seal arrangement of  claim 18 , wherein the abradable coating is made from a metallic material.